Curious about the science of barrel aging whiskey? You’re not alone! While this is a tremendously multivarite process, we’ve broken it down to be easily digestible.

It’s important to note that changing the variables we discuss give drastically different outcomes in the final product. Up to 70% of the final flavors and fragrances found in whiskey are formed within the relationship between the new make spirit and the barrel. It is vital that we do our best to understand this relationship in order to make the best product possible.

As technology advances, people look for shortcuts in the process of aging whiskey, such as smaller barrels, different barrel treatments etc. We stick to traditional methods to  create great whiskey – our core mission as a company.

A CLOSER LOOK AT THE COMPOUNDS:

Whiskey barrel science is concerned with a small group of compounds that affect the outcome of whiskey.

• The first compound to recognize is called Cellulose. This helps to create a tight bond holding the wood together. This compound, however, has very little effect on the whiskey itself.
• Possibly the most important compound is the Hemicellulose. Upon exposure to extreme temps (284F or more), it begins to break down into wood sugars. This allows for caramelization on the interior surface of the barrel.
• Lignin is also a very important piece to this puzzle. It’s responsible for the vanilla and spice flavors commonly found in whiskeys. The more a barrel is charred, the more lignin compound yields notes of spice and smoke.
• Tannins in the fresh wood can be a lot to handle. To rid the oak of some of these extreme tannins, we allow the wood to “season” or dry out. As the process continues, the higher the char of a barrel, the less interaction between spirit and tannin occur.
• The last compound on our list, wood Lactones, pertains to American oak in particular. American Oak sees higher concentrations of this element than other barrel species. This is responsible for the woody/coconut notes you may experience in some whiskeys. It could also be found in wine that was aged in American oak like Rioja, most famously. Like tannins, the higher the char levels, the less of an impact they have on the spirit aging within the barrel.

THE DIFFERENT VARIABLES THAT OCCUR WHEN A BARREL IMPARTS THEM INTO THE SPIRIT:

There are four main variables to account for during the aging process.

1. Extraction. As temperatures begin to rise in the summer, the spirit in the barrel warms and expands. This increases the pressure inside the barrel and forces the spirit deep into the porous wood. As the season changes to fall and winter, the temperature and pressure begin to drop. The spirit is forced back out of the wood, bringing these flavor components with it. The more cycles the spirit to goes through, the more flavor will be extracted.
2. Oxidation is another huge part of flavor enhancement and development. It’s argued that oxidation increases the complexity and intensity of flavors. In large, it is responsible for the fruity, spicy, minty notes sometimes found in some whiskeys. Oxidation, however, needs help from the new make spirit itself to create flavors. These flavor compounds react with the oxygen to create new flavors. The more complex the spirit is before maturation, the more oxidation helps influence these flavors and characteristics as time goes on.
3. In barrels experience a charring effect, we not only notice addition of flavors, but subtraction of flavors as well. If you’ve ever had a water filter and witnessed the black specks of carbon floating around, there is a similar effect happening inside the charred barrel. Once the spirit enters a charred oak cask, the interior surface begins to act as a charcoal filter. In the case of whiskey, this filter is mainly subtracting sulfides, which causes some unpleasant metallic, gunpowder tastes. Some of these unwanted elements are also subtracted through evaporation over time.
4. While we can explain much of the science behind it, there is still an element of unpredictability to the whole process that remains a mystery. For instance, you can have two casks filled on the same day, with the same spirit. They could sit next to each other for the duration of their lives in barrel. In the same style barrel, made from the same wood and receiving the same internal treatment, and they will still produce different results. It’s a mystery that has plagued the industry professionals since we first put spirit into barrel. The magic of oak maturation keeps us driven to learn and taste to better understand the unique characters of our spirit in barrel.

HOME SWEET HOOD RIVER

At Wanderback, we’re blessed to call Hood River our home. The climate, temperature cycles and humidity levels are perfect for aging whiskey. In our barn, we create our own microclimates by moving barrels to the warmer second level of the barn to speed up the process. The lower level maintains a cooler cellar temp that allows a slower/more controlled aging environment.

As for barrel selection, we only use American oak air dried for 3 years out in the elements. This process helps us hit the taste profile we are looking for in our whiskey by removing just enough wood tannin. Coopers dry anywhere from 12-48 months, but for us, that 36 months of drying gives us what we are looking for. For our whiskeys, we find the perfect balance in barrels that have been heavily toasted and lightly charred. By aging our whiskeys in new oak barrels with these treatments, we get the perfect balance of complexity and flavor. These also provide the texture we are seeking on the palate.

OTHER FACTORS TO CONSIDER:

Another important element to note for the science of barrel aging is the alcohol by volume (ABV) of our spirit upon entering the barrel. Lower ABV promotes dissolving the more water-soluble flavors. For us, that means barreling at 60% ABV, or 120 proof, as a balance between water soluble and non-soluble barrel components. Typically, our new make spirit comes off a still around 140 proof so a little dilution before barreling is necessary to achieve this. This achieves a balance between the complexities already found in the new make spirit and the flavors developing and forming through this process.

We only use 53 gallon new American oak barrels for the first 3 years of the aging process. In comparison to others that use the same size barrels, this allows for a faster aging process than more traditional Scottish single malts that go straight into used bourbon barrels. This use of Virgin oak is a common tradition amongst American whiskey producers.

CANTON VS. ISC BARRELS

To understand all the differences that occur inside barrels with two different treatments, we’re currently tracking a spirit we made in Texas that has been in barrel for just over a year now.

The differences in these barrels lie in the amount of air drying the wood received (Canton 2 year ISC 3). The treatment on the inside of the ISC Level 1 char High Toast vs. Canton just high toast and the higher levels of oxidation that occur due to the tightness of the grain and craftsmanship of the barrels. Canton is very tight, where ISC allows for a bit more breathing.

The Canton barrel shows much lighter notes consistent with honeycomb, graham cracker, rose petal, marshmallow and smells of banana and papaya. ISC barrel is drastically different right up front with bolder notes of savory toffee, powdered cocoa and baking spice.

As time passes, we expect the color of the spirit in the ISC barrel to darken into a traditional brown. The Canton barrel, however, should deepen along the golden spectrum.